Examining Ribosomal Localization based on Microtubule Polarity in Drosophila melanogaster Neurons

Open Access
Author:
Lee, David Francis
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Melissa Rolls, Thesis Supervisor
  • David Scott Gilmour, Honors Advisor
Keywords:
  • Neurons
  • Drosophila
  • Ribosomes
  • Microtubules
  • Rolls
  • Lee
  • Fluorescent Microscopy
  • Developmental Biology
  • Biochemistry
  • Molecular Biology
  • Neuroscience
  • Trafficking
Abstract:
Ribosomes are crucial to cellular function and development, as they are responsible for translation of mRNA to produce proteins that are vital to life; this holds true in neurons because they must be preserved for an organism’s entire life. Understanding ribosomal localization in neurons can help build the framework to answer key questions about regeneration and disease, especially when comparing axons and dendrites. Interestingly, the localization is differentiated based on the neurite extending from the cell body in a plethora of organisms; ribosomes accumulate in the soma and dendritic branch points, but not the long axon, of Drosophila melanogaster dendritic arbor (da) neurons. This body of work aims to uncover how exactly ribosomes are being trafficked to dendritic branch points. Different approaches were utilized to do this, including the knockdown of a motor protein and the disruption of normal microtubule polarity to yield scenarios differential to the uniform polarity of the Drosophila neuron. I uncovered that the knockdown of Dynein, which is the minus-end-out motor protein, significantly decreased ribosomal localization in the dendritic branch points. Furthermore, uniform minus-end-out microtubule polarity in the dendrites was altered by both knocking down a microtubule stabilizing protein and inducing the change to plus-end-out polarity via axon injury to determine if this affected ribosomal localization. In both such cases, it was determined that ribosomal trafficking was decreased in branch points that had increased plus-end-out character. Each experiment supports the hypothesis that ribosomal trafficking is dependent on minus-end-out microtubule polarity. This can lead to insight on differential means of regeneration and upholding between axons and dendrites, as well as help explain the localization of different organelles and crucial proteins that behave in the same manner.